Well controlled tissue removal can be an important aspect of surgery. In at least some instances the ability of a surgeon to perform an incision without substantially affecting the surrounding tissue, for example the tissue adjacent to the resection site, can be clinically helpful. For many surgical procedures, it would be beneficial to avoid, or at least decrease, injury to the adjacent tissue. Furthermore, it can be beneficial for a surgeon to use a resection tool that is capable of reaching a remote surgical site, such as a treatment site accessed endoscopically.
A variety of tools have been developed to remove vascular soft tissue, cartilage and bone during surgical procedures, and many of these prior tools can be less than ideal for tissue cutting, for example of an internal surgical site. Mechanical instruments such as scalpels, biters and curettes along with powered mechanical instruments such as microdebriders and drills have been employed. Mechanical devices may cut tissue with varying degrees of localization and in at least some instances can induce mechanical trauma to the tissue. Although energy delivery based devices such as radio frequency, ultrasonic, and lasers have been used for tissue removal, these devices can have disadvantages in at least some instances. For example, when tissue is inadvertently removed or damaged by mechanical or thermal injury the clinical outcome and patient recovery can be adversely affected in at least some instances.
Radio frequency (RF) devices have been for tissue removal, and the prior RF devices can result in less than ideal tissue cutting. Although RF devices can be used to cut tissue by thermal and/or plasma mediated mechanisms, RF devices can cause at least some level of thermal injury in the adjacent tissue in at least some instances. In at least some instances, thermal injury may occur to the tissue adjacent to the cut. Also, RF devices can introduce accessibility and maneuverability challenges for surgeons, such as endoscopic surgeons in at least some instances.
Although prior laser based energy devices have been used for tissue removal, these laser systems can cut tissue more slowly than would be ideal and can injure the tissue adjacent to the cut. For example, thermal injury can occur in the tissue adjacent the cut with at least some commercially available medical laser systems. In at least some instances, the prior laser systems can be characterized by a Heat Affected Zone (HAZ) in front of an ablation zone. The laser energy can be introduced to the target tissue over time sufficient to raise the temperature and ablate tissue. In at least some instances the ablation process can be accompanied by charring of collateral tissue along with a significant HAZ which can be detrimental to the healing process. Although some pulsed laser systems such as UV, photospallation, and ultrashort pulse laser systems may ablate tissue with somewhat decreased thermal damage as compared to continuous wave systems, in many instances pulsed laser systems may not cut tissue quickly and an ablation plume can interfere with a subsequent laser beam pulses such that increasing the rate of laser beam pulses may not adequately increase the rate of tissue removal in at least some instances.
Although UV based laser systems such as excimer laser systems have been used for tissue ablation, the UV based systems can have a shallow per pulse penetration depths and may result in tissue mutagenic effects in at least some instances. The pulse rate and shallow depth per pulse ablation depths can make UV based laser systems less than ideal for tissue removal in at least some instances. Also, the light from UV based laser systems can have less than ideal delivery through optical fibers, such that access to internal surgical sites can be limited in at least some instances. The generally slow overall depth penetration ablation rates, limited fiber delivery, and complexity can make UV laser systems less than ideally suited for tissue resection requiring larger cuts, in at least some instances. For example, with endoscopic surgical procedures light energy is delivered through an optical fiber and tissue is cut to a substantial depth along a substantial length, such that UV excimer laser systems are not well suited for endoscopic tissue cutting in at least some instances.
Although prior pulsed infrared lasers have been used to ablate tissue with photospallation, photospallation can be less than ideal for cutting tissue in at least some instances, such as endoscopically. Photospallation can have shallow per pulse ablation depths, such as a few microns, and photospallation based systems can have pulse rate limitations, such that the overall tissue cutting rate may be too slow for practical use. Also, photospallation systems can use optical wavelengths that are strongly absorbed by optical fibers, such that delivery to internal surgical sites on a patient may not be possible. Photospallation systems can be less than ideal for tissue resection due to very slow cutting rates and no practical means to deliver the laser energy for most endoscopic procedures.
Although prior ultrashort pulse laser technology such as femtosecond and picosecond laser systems can ablate tissue with an ionization process, the total energy per individual pulse can be very small and result in small amounts of tissue ablated. Also, the high peak powers can be unsuitable for fiber optic waveguides in at least some instances. Therefore, ultrashort pulse lasers can be less than ideal for tissue resection with larger cuts, such as in endoscopic surgical procedures.
Therefore, it would be helpful to provide improved methods and apparatus for cutting tissue that overcome at least some of the above limitation of the prior systems. Ideally, such methods and apparatus would provide surgeons a fast and effective cutting tool with flexibility to perform many sizes of tissue resections with precise localization, including cutting tissue without substantial thermal or mechanical damage on the tissue adjacent to the cut, for example. It would also be helpful if such methods and apparatus could accurately cut tissue without substantial tissue damage at an internal patient location with a flexible waveguide, for example with a flexible silica fiber for endoscopic procedures. Additionally methods and apparatus for tissue cutting that are applicable to a broad variety of tissue types may be important to surgeons and/or necessary to effectively perform certain procedures.